Treating hypertension in black compared with white non-insulin dependent diabetics: a double blind trial of verapamil and metoprolol.
STUDY OBJECTIVE: To compare responses of blood pressure to the calcium antagonist verapamil and the beta blocker metoprolol in black compared with white diabetics with hypertension and to monitor urinary albumin excretion in relation to fall in blood pressure. DESIGN: Double blind, placebo controlled, random order crossover trial with four week placebo run in period and two six week active phases separated by a two week placebo washout period. SETTING: Outpatient department of a general hospital in a multiethnic health department. Patients--Diabetic patients with hypertension. Four dropped out before randomisation; 25 black and 14 white patients completed the trial. INTERVENTIONS: Patients given slow release verapamil 120 mg or 240 mg twice daily with placebo or metoprolol 50 mg or 100 mg twice daily with placebo. Treatment for diabetes (diet alone or with oral hypoglycaemic drugs) remained unchanged. END POINT: Comparison of changes in blood pressure in the two groups taking both drugs. MEASUREMENTS AND MAIN RESULTS: Metoprolol had little effect on blood pressure in black patients (mean fall 4.0 mm Hg systolic (95% confidence interval -2.5 to 10.4 mm Hg), 4.3 mm Hg diastolic (-0.8 to 9.5)) but more effect in white patients (mean falls 13.4 mm Hg (0.1 to 26.7) and 10.6 mm Hg (4.5 to 16.7) respectively). Verapamil was more effective in both groups, with mean falls of 8.8 mm Hg (2.4 to 15.0) and 8.1 mm Hg (5.0 to 11.2) in black patients and 19.1 mm Hg (5.4 to 32.9) and 11.4 mm Hg (0.9 to 22.0) in white patients. Heart fate fell significantly in black patients taking metoprolol, which suggested compliance with treatment. Metabolic variables were unaltered by either treatment. Plasma renin activity was low in both groups after metoprolol treatment, but change in blood pressure could not be predicted from baseline plasma renin activity. Urinary albumin:creatinine ratio was independently related to baseline blood pressure but not significantly changed by treatment. CONCLUSIONS: beta Blockers alone are not effective in treating hypertension in black diabetics. Verapamil is effective but less so than in white patients. As yet no ideal monotherapy exists for hypertension in black patients.